Multi clinker fireclay bricks are refractory bricks with more than 80% clinker and less than 20% bonding clay. 

Since most of the raw materials are in a barren state, the bricks are not easy to deform and can maintain a precise size. The finished products have ideal bulk density, mechanical strength and thermal shock resistance. The raw materials contain a low content of bonding clay. This makes the molding of bricks a little difficult. In addition to using brick pressing machines with higher pressure, electrolyte or gelled substances (e.g. sulfite waste paper pulp, resin, pitch, cellulose, etc.) are added into the raw materials to enhance the bonding properties of the materials. 

Soft clay with good plasticity is an ideal binding agent for multi clinker fireclay bricks. It also has good dispersion, so it can fully adhere to the surface of clinker particles and produce better bonding force. Pre-wetting the clinker with mud can also improve the bonding properties of mud. 

The particle selection of multi clinker bricks is different that of the common fireclay bricks. In order to achieve the dense bonding with fewer materials, the composition of particles and the critical grain size of coarse particles play a decisive role. In order to reach the desired bulk density, attention must be paid to the following factors: 

(1)    The particle size should be controlled in a minimum range. (2)    The content of fine particles increases until all particles are bonded firmly together and fine particles and bonding clay can fill in the coarse particles. 

(3)    Appropriately increase the critical size of the coarse particles. The water absorption rate of clinker particles should be under 3%. There should be a certain proportion of fine particles smaller than 0.088mm, because fine particles can fill gaps in the materials and increase the sintering properties and barren state of raw material and reduce the shrinkage during the firing process. Particles with acute angles are ideal. Fast crushing can increase particles with acute angles. 

When preparing mud, first make bonding clay into mud no lower than 50℃. Then add clinker and knead. Place the mixture in an environment with a relative humidity of 60% below 20℃ for 24 hours. The molding pressure should be more than 300kg/cm2 (2.94x107 pa). Large bricks more than 30kg are generally molded by vibration molding or air hammer tamping. 

The firing temperature should be more than 1450℃. When firing in a tunnel kiln, the higher the temperature is, the faster the rotational speed is. If the maximum temperature is 1380℃, the pushing time of the kiln cars is 2h. If the maximum temperature is 1400℃, the time is one hour 40 minutes. If the maximum temperature is 1500℃, the time is one hour. This can improve the utilization coefficient of the kiln and save energy. When firing in a down-draft kiln, a reasonable temperature curve should be made. Blow 600℃, the temperature should rise slowly at 20℃/h, or too fast discharging of residual water can cause cracks or deformation. Above 800℃, there are only structural changes, the temperature can rise quickly. When reaching the desired temperature, maintain it for 5-10 minutes.